Case-hardening process.



A. W. MACHLET.

CASE HARDENING PROCESS.

APPLIOATION FILED 10110.19, 1911.

Patented Aug. 11; 1914.

To all whom it may concern;

Elizabeth, in the county of Union and State ADOLPH W. :CHLET, OF ELIZABETH, NEW JERSEY.

UASE-HARDENING PROCESS.

l,ll6,5?3.

original application filed May 25, race, Serial Ito.

Specification of Letters Patent.

Patented Aug. ill, rare.

318,679. Divided and this application filed December 19, 1911. Serial Ito. 886,651).

Be it known that l, ADOLPH W. MAcminT, a citizen of the United States, residing in of New Jersey, have lnvented certain new and useful Improvements in Case-HardeningProcesses, of which the following is a specification.

This invention relates principally to casehardening steel or iron articles.

7 lnflPatent No. 822,460 is set forth a mannetor case-hardening by inclosing articles in a retort, and both heating and rotating the retort while a current of carburizing gas circulates therethrough; and in Patent No. 884,180 disclosed a manner of thinning the carburizin as by means of ammonia.

@ne of the o ]ects of the present invention is to simplify and reduce the cost of the heating apparatus and the operation thereof, as well as to adapt the same forcertam kinds of work, andjanother object is to provide for seclning the roper quality of carburizing gas, as we as for diluting the same, whereby the user ma operate independently or the ordinary' umlnatmg gas supply, which is not always available, and which in some cases is not suitable for carburizing. y 1

Accordin to the first part of the present invention, t e articles are placed directly in the flame chamber'of a retort which is in the form of an oven, and heated directly'by the flames, and then the mes are extnn ished, and the oven'is filled with carburizin gas, which cements thearticles by means 0 their own retained heat. The walls of the oven are eatly thickened for the 1 "pse of retaimng heat, thus delayi 1 the ceomg of the articles suficiently to enale themto be substantially cemented by their retained heat, or by the heat retained in the oven. The-top of the oven is rovided with pne or more capacious vents or the escape 0t products of combustion during the heating 0? the articlcs, and these vents are provided with closures, whereby they may be closed during the subsequent carburizing o eratlon and the oven is also provided wit a constricted regulatable vent forcontrolling the flow of carburizing gas th ou h. The carburizing s is prerably introduced into the oven t rough the same pipe which feeds the burners. In practising. the second part of my inven- ,ent tor the available,

tion, which may also be used in connection with other carburizing heaters, such for instance ,as the revolving retort shown in said Patent No. 822,460, ammonia gas is led from a tank through a body of naphtha, the ammoma taking up a quantity of naphtha, and being led into the retort or oven to carburize the articles; the ammonia serving as a dilucarburizing gas which it derives from the naphtha, and avoiding the deposlt of free carbon upon the articles, and hastening the carburi'zing operation. By this means, the user becomes independent of the supply of illuminating or heating gas from the usual sources, which is liable to fluctuate in quality, or which may not be and is assured a continuous supply of carburizing gas of uniform quality.

()ther objects, features and advantages will hereinafter appear.

In the accompanying drawings, Figure 1 shows one form of apparatus operating in accordance with my present invention; portions of the oven and the oil tank being broken away to disclose the construction. Fig. 2 is'a cross-section of the oven, showing the burners let into the opposite walls thereof.

The oven comprises side walls 1, 2, rear walls 3, top 4, front wall 5 and base 6, all made of refractory material and greatly thickened in proportion to the capacity of the oven, sot-hat they retain heat, thereby to delay the cooling of the articles, and

hence prolong the cementing operation un til a. substantial shell is formed upon the articles. The oven is preferably contained in an iron boxing 7, and restsupon an iron base 8 supported upon legs 9. At the front of the oven is provided a door or lid 10 of thick refractory material, which may be lifted by means of hooks 11. In the top of the oven are provided capacious vents 12, which are made open during the generation of flames in the oven and may be closed by conical lugs 12 duri the subsequent filling of the oven with car urizing gas. I

Gas or other fuel su plied to the oven through a pipe 13 contro ed by a valve 14; and air is supplied through a pipe 15 controlled by a valve 16", the air being pret. erably su plied'derpressure. The mixed air and rel are distributed by means of pipes 17, 18, it and 2b, to burners 21 in the base of the oven." Preferably the burnersjlip are arranged in two series in the opposite walls 1, 2, so as to direct the flames along the floor 6 of the oven. A thick plate 22 of either iron or refractory material may lie horizontally just above the burners, spaces being left at 23 around the edges of the screen for the passage of flames up into the body of the oven, whereby the flames are caused to heat the walls of the oven very hot, as well as articles contained therein. The screen also because of its great thickness serves as a reservoir of heat effective to prolong the carburizing operation.

In operation the door 10 is lifted and the articles 24, such as tubes, or bars or devices of any shape are placed upon the screen or table 22. Before the door 10 is dropped, the valves 14 and 16 are opened and the mixture of the gas and fuel is ignited at the burners 21, the products of combustion escaping through the vent or vents 12. The heating proceeds until the articles reach a carburizing heatwhich is say above red heat and below the melting point; at which time the door and the walls of the oven, as well as the screen 22, are heated to about the same temperature as the articles, and serve as reservoirs of heat to prolong the carburizing operation. Thereupon the valve 16 is closed to cut off the air and extinguish the flames at the burners, and the vents 12 are closed by the plugs 12; and gas may continue to flow in through the pipe 13 to immediately fill the oven and carburize the articles; this gas being of any suitable quality, as coal gas ,or any other carburizing Preferably a constricted vent pipe 46 is fitted in the lower part of the 'door 10 or one of the walls of the oven, so that the current of carburizing gas may pass slowly tlfifrou h the oven, thus insuring the drawing 0 0 through the pipe 13 of fresh gas. This vent may be regulated by a valve 47. The gas escapingthrough this vent and igniting in the air shows its condition by the color of its flame. The operator is hence enabled to control the condition and flow of the gaseous atmosphere in the oven by regulating either valve 47 or 14 or both. Owing to the thickness of the heated walls, the cooling of the metal articles is greatly delayed, and they are enabled to become. cemented to a substantial depth by means of their own retained heat, or by means of the heat retained in the oven. After thearticles cool to a certain extent, the chemical action of the gas thereon ceases; and they may then be removed from the oven or retort and immediately replaced by other articles, so that the operation of heating may be repeated before the walls of the oven have lost a great amount of heat. In case the cementation does not proceed to a suflicient depth,

the vitiated gas, and the renewal they may be allowed to remain in the oven, and the valve 16 may be opened to admit air, and the oven again heated as before by raising the articles to the carburizing point, whereupon the flames may be again extinguished and carburizing gas supplied to the oven, thus causing the cementation of the articles to proceed to a greater depth; and this operation may be repeated on the same articles until they have the required depth of cementation.

' Ammonia or other inert gas may, if de sired, be admitted through a pipe 48 which joins the pipe 17, and is provided with a valve 49, the latter being closed during the operation of heating the oven. The mixture of gas and ammonia may be controlled by said valve 49; or other means may be provided for securing a supply of diluted gas to the oven. It will be seen that not only the burning mixture, but also the carburizing gas, with or without its dilutant, are admitted through the burners; but the carburizing gas either diluted or not may be otherwise introduced into the oven.

In case the heating "gas is not of a quality suitable for case-hardening, or if no gas is available from ordinary sources for the purpose of carburizing, the devices now to be described may be employed. A tank 50 is nearly filled with naphtha 51. A' tank 52 containing ammonia or other suitable inert gas under pressure, is put in connection with the tank 50 by means of a pipe 53, the flow of ammonia being controlled by a valve 54 in said pipe. The latter extends down into the oil tank 50, and terminates near the bottom thereof in a spray 55. Bubbles of ammonia are seen at 56 rising from the spray, and during this action they take up a plenum of naphtha or carbon filling the top of the tank 50 with gas comprising am-. monia and carbon. This gas may be led through the pipe 48 from the top of the tank 50 through the pipes 17, 18 and 19, and into the oven through the burners 21; the valves 14 and 16 bein closed and the flames extinguished. Preferably the proportion of ammonia which entersthe retort or oven is large relatively to the proportion of carbon to the carburizing fluid, so that deposit of surplus carbon upon the articles is avoided or at least reduced to such an extent as to be insignificant, while the process of carburizing is much hastened, thereby saving fuel, while a uniform shell of very high quality is produced. Little if any more carburizing gas is admitted to the retort than is readily-taken up by the iron or steel articles therein.

In order to maintain a suflicient quantity of naphtha or other suitable mineral oil in the tank 50, it may be connected by a pipe 57 to a reservoir 58 above the tank. In the latter may be placed a float 59 attached to a lever 60 controlling a valve 61, which regulates the flow of oil from the reservoir into the tank. The latter may alsobe provided with a gage glass 62. The herein shown described method of passing ammonia through the naphtha may be employed in connection with other retorts or carburizing apparatus.

The invention is particularly useful in the case of rifled guns or other arms, since the barrels of these implements may be made of soft steel, and readily rifled and finished, and then hung up by their ends in an oven or retort and case-hardened by the method herein shown or by that shown in my said pending applications. As a result, the life of the arms will be very greatly prolonged because the rifling in the barrels, being hard, will not be injured by the projectiles; while the double tube of hard steel, one on the outside, and the other on the inside of the barrel will improve the rigidity and accuracy thereof.

When desired articles may be forged in the usual manner, and then while still hot placed in the oven or retort, and a mixed current of carburizing gas and ammonia caused to flow through the retort, so that a single heating may suflice for both forging and case-hardening the articles. This will be of great advantage especially. in the case of anvils and other heavy articles. If a forged article when placed in the oven is a little too cool for case-hardening, the gas and air may be temporarily'turned on at the valves 14, 16, until the article is brought up to the required heat.

Variations may be resorted to within the scope of the invention, and portions ,of the improvements may be used witliout others.

This application is a division of my application No. 318,679, filed May 25, 1906.

Having thus described my invention, I claim:

1. The process, of case-hardening consisting in confining in an oven the articles to be case-hardened, producing flames in said oven to heat both the oven and the articles, ex

tinguishing the flames and then introducing gas into the oven to case-harden the articles by means of the heat retained Within the oven. a

2. The process of case-hardening steel or iron articles, consisting in confining the articles in a .heat retaining oven, producing flames in the oven to heat the same and the articles, until the latter reach carburizing heat, andjthen extinguishing the flames and causing a current of carburizing gas to pass through the oven.

3. The process of case-hardening a steel or iron article, consisting in first heating the same to a carburizing heat by the direct play of flames thereon, and then exposing it while out of contact with flame to an atmosphere of carburizing gas, to cause the article to joecome cemented by means of.its retained ieat. 4

4. The process of case-hardening a steel or iron article, consisting in first heating the same to a carburizing heat and exposing it while cooling to an atmosphere of carburizing gas, to cause the article tobecome cemented by means of its retained heat, and causing the cooling to be delayed during the carburizing process.

5. The process of case-hardening steel or iron articles, consisting in heating them to carburizing heat, exposing them to carburizing gas while they are slowly cooling, re-

heating them, and' again exposing them to carburizing gas While slowly cooling.

6. The method of case-hardening, comprising the following: applying flames directly to the article to be case-hardened while said article is confined in a furnace, then extinguishing the flames while the article remains confined in the furnace, andthen introducing suitable gas into the furnace to case-harden the article by means of the heat retained in the article and in the walls of the furnace.

7 The method of case-hardening an article, consisting in applying flames thereto while the same is confined in a manner to insure such retardation of the loss of heat therefrom, after the extinguishing of the flames, as would render the same self-cement ing, then extinguishing the flames, and subjecting the article immediately to a current of carburizing gas- 8. The herein described process of heatforging articles and carburizing them while still heated from the forging operation while out of contact with flame and While it continues to be confined as aforesaid.

ADOLPH W. MACHLET.

Witnesses:

SAMUEL R. OGDEN, JOHN J. soon. 

